Pattern repeat length control system

ABSTRACT

Digital inputs are fed to a programmed digital computer for a precise measurement and calculation of key line-speed parameters. The ratio of the web infeed speed measured at a point upstream of all processing actions relative to the embossing roll speed is the controlled variable. Digital speed recorders measure the web infeed speed and the embossing roll speed. The relationship between these two is automatically manipulated by the digital computer which reflect the process dynamics and describe the desired system response.

United States Patent Horst et al. [45] Sept. 26, 1972 54] PATTERN REPEATLENGTH 9 3,257,086 6/1966 Drenning ..242/75.4

CONTROL SYSTEM 3,428,877 2/l969 Campbell et al ..3 1 8/85 [72]Inventors: Robert L. Horst; Richard M. 3559568 2/1971 Ringer, both ofLancaster, Pa.

Armstrong Cork Company, Lancaster, Pa.

Filed: Aug. 16, 1971 Appl. No.: 171,849

52 u.s.c1. ..23s/1s1.1, l0l/l8l,3l8/85,

- 226/42 1m. 01. ..B65h 23/20 Field of Search ..31s/ss; 101/181; 226/42;

[56.] References Cited UNITED STATES PATENTS 2,999,295 9/1961ManningetaL ..226/42x Stanley ..l0l/l8l Primary Examiner-Eugene G. BotzAttorney-Clifford B. Price ABSTRACT Digital inputs are fed to aprogrammed digital computer for a precise measurement and calculation ofkey line-speed parameters. The ratio of the web infeed speed measured ata point upstream of all processing actions relative to the embossingroll speed is the controlled variable. Digital speed recorders measurethe web infeed speed and the embossing roll speed. The relationshipbetween these two is automatically manipulated by the digital computerwhich reflect the process dynamics and describe. the desired systemresponse.

3 Claims, 2 Drawing Figures 10 2, W i! O v v V V x LINE r. DIGITAL RATIOMEA(.suREM)ENT Xr xr 1'40 CONTROL PATENTEUszrzs 1912 v 3,694,634 SHiIETI 0F 2 A V ATTORNEY PA'TENTEB SEP26 m2 ABORT SIIEEI 2 III 2 SYSTEMREAD RATIO CYCLE SET POINT DIFFERENCE RESPONSE COMPARISON (0.) ICOEFFICIENT (b) WITHIN DEADBAND OUTSIDE l RANGER) ABORT INSIDE ALARMOUTSIDE l LIMITSQ) I OPERATES ABORT ALARM MAX. DELTA R G) MOTOR VOLTAGECOEFFICIENT (d) f CONTROL SIGNAL AMCIQL ATTORNEY BACKGROUND OF THEINVENTION 2. Description of the Prior Art Various systems are known atpresent for controlling repeat length. These systems characteristicallymonitor and control independently a number of different factors such asweb tension, temperature, web speed, etc. On the basis of one or all ofthese factors, a control is effected which can be achieved to a maximumaccuracy of about plus or minus 0.5 percent. Other systems are availablewhich attempt to hold the sheet material or webs in a relativelystress-free state so that no stresses are developed within the sheet tocause variations in the repeat pattern.

With a number of the earlier designs placed on the semi-flexible webswhich were used primarily as floor coverings, there was no great need tohave exact precision in any repeat pattern. The patterns were such thatwhen two sheets were placed side by side there was no need for registrybetween the patterns. on adjacent sheets. However, at this time designrequirements have now reached the stage that registry between adjacentsheets is necessary. Therefore, it is necessary that the repeat patternlength be accurately controlled so that when a 50 feet long web is cutin half and the two 25 feet pieces are placed side by side, the patternalong the adjacent edges will match for the whole 25 feet length of thesheet. Should there not be match, the aesthetic effect of the pattern isdestroyed.

SUMMARY OF THE INVENTION Control of the pattern repeat length isaccomplished by controlling the speed of the embossing roller. The speedof the embossing roller is controlled based upon monitoring of two keyfeatures. There is monitoring of the web speed Xr upstream of the firstprocessing roller at a position where the web is well behaved, that is,at the infeed end of the processing line. There is also the measuring ofthe embossing roll speed Xr. The ratio (Xm/Xr) of the upstream web speedto the embossing roll speed downstream is used to control the embossingroll speed. By the measuring of just the two above factors, a simplifiedsystem is provided. Digital means is used to measure the two factors tohigh precision 002 percent) and to determine the ratio of them.

Pulse generators are connected to the embossing roll and a disc whichengages the web upstream of the first process roller. Both embossingroll and web speed are developed by this means and fed to a digitalcomputer. A control with a series of variables is used to read the ratioof web speed to embossing roll speed, to determine the ratio error, andthen to control the ratio to maintain it at that point which providesproper uniform repeat pattern length.

BRIEF DESCRIPTION OF THE DRAWING FIG. I is a schematic drawing of theprocessing ap paratus; and

FIG. II is a simplified data-flow diagram for the computer controlsystem.

DESCRIPTION OF THE PREFERRED EMBODIMENT An existing line for theprocessing of a sheet flooring material was analyzed. The sheet formingmaterial and its general mode of manufacture are set forth in U. S. Pat.No. 3,l48,076. The smooth laminating roll of the patent has beenreplaced by an embossing roll as is conventional in the art. Amathematical model of the entire processing line was developed. Themathematical analysis involved the measuring of a number of differentincremental speed factors along the web at positions between the variousprocess stage. A series of process factors were incorporated within themathematical analysis. On the basis of the different measurements anddifferent factors, a mathematical expression was developed to define themanufacturing operation which will provide for controlled repeat lengthpatterns. From the mathematical analysis and its application to theexisting processing line, it was determined that one particular factorprovided a control medium which was sensitive to all the other variablefactors. The particular factor which could be used along to control theembossing roll feed is the relationship of the upstream web feed to theembossing roll speed downstream thereof. By the measuring of these twospeeds and maintaining their proper ratio, the normal control system isconsiderably simplified in that it avoids the need to measure all of themany different factors which had been taken into account separatelyheretofore. However, digital means must be used to measure the twofactors and to determine the ratio therebetween so that the embossingroll speed can be controlled to a very high degree of accuracy toachieve the uniform pattern repeat length.

Referring now to FIG. I, there is shown the overall processing system. Aconventional infeed accumulator 2 is used to collect a substantiallength of web material from a roll of web material. The infeedaccumulator provides for a continuous operation. Material is rapidly fedoff one roll of material into the accumulator. During the time that asecond roll is being positioned and spliced to the first roll, the totalprocessing apparatus will be pulling collected material from theaccumulator. This will provide for constant flow of web material throughthe processing apparatus.

The web material 4 is fed from the accumulator by appropriate rollstructures to a horizontal plane where the processing of the webmaterial begins. A hopper 6 with a conveyer 8 deposits chips of plasticmaterial onto the upper surface 10 of the web material. Vibrators 12then vibrate the web to secure a uniform coating and distribution of thechips across the web material. The web material with the chips thenpasses to a heating station 14. The chips are heated to soften them suchthat they will adhere to the web and at the same time take the embossingwhich is going to be provided by the embossing roll 16. The embossingroll 16 is backed up by an appropriate back-up roll 18. From the pointwhere the chips are placed on the web until the web and chips passthrough the embossing roll 16, there is performed what is called theupstream processing 20.

After the upstream processing 20 is performed, the embossed sheet thenpasses to downstream processing such as a cooling area 22 where thesheet is permitted to cool by being passed over a series of rollers in acooling atmosphere. The web than passes on down past point 24 through aseries of further processing steps. These further processing steps caninclude the application of further material to fill in the embossedareas with a clear coat, the application of heat and further laminatingpressures, etc., until such time as the sheet is returned to a cooledstate which will permit the sheet to then be placed upon a roll in itsfinished state.

The invention herein is directed primarily to the provision of a pulsegenerator 26 which is positioned ahead of the upstream processing 20 todetermine the line speed (Xr,,of the web in its unprocessed state. Herethe web is at ambient temperature and uniform tension and has beenunaffected by any processing operation. The web speed is measured andfed into a digital ratio rrieasurement and control system 28. At thesame time, a second pulse generator 30 is connected to the embossingroll to provide readings of the surface speed (Xr) thereof. The datafrom element 30 is fed to the digital ratio measurement and controlsystem 28 which operates to compute the ratio (Xr /Xr) and to thencompare it with a set point to determine whether the embossing rollspeed should be changed. If it is determined that the embossing rollspeed should be'varied, the digital control provides a control signal tothe embossing roll differential 32 to vary its speed. The signalcontrolled differential may be a conventional differential such as theSpecon Draw Transmission of Fairchild l-liller. A motor 34 drives theembossing roll 16 through the differential 32. Y

The digital computer, used to compute the ratio (Xr /Xrb) and to usethat ratio in comparison with various preset parameters, can be any typeof conventional digital computer.,Specific operations have been carriedout by the use of the Hewlett Packard Computer No. HP-2l 143 used inconjunction with the digital recorder HP-5050B (used to store presetparameters). The computer and recorder system has seven adjustableparameters. The following 'is a list of the parameters, their range andthe typical value at which they were actually set during a normalcontrol cycle.

System Cycle'Coeff. (.5 50) These parameters and their relationship toone another are indicated in FIG. ll.

The set point a is the control point at which the ratio The responsecoefficient b is a gain control feature which is utilized to optimizethe control system response. The responsecoefiicient b is used in effectas an overall gain control for the system so that the system functionswith a fairly even constant response.

The dead band range .0 represents the range of ratios deviating from theset pointa in which no error correction is made. The purpose here is toeliminate the need for making very minor adjustments.

The motor voltage coefficient d is the voltage adjustment feature whichis used to establish the speed of change of the control motor'(part ofdifferential) for the embossing roll 16. It is a setting of themagnitude of the correction which will be made to the control motor.

The alarm limit 2 is the range beyond which the deviations between thecomputed ratio and the set point will set off a visual and audiblesignal to direct the controller's attention to an excessive error. Eventhough the apparatus will compensate for errors, it is necessary that anoperator have his attention directed to the fact that substantial errorsare occurring.

The maximum delta R, parameter f, represents the maximum incrementalstep which can be taken during each cycle of operation to alter a ratiooutside of the dead band back to a ratio within the dead band range. Fora given error, there will be a certain desired change in the ratio. Thelimit of this change can be varied by varying parameter f, the maximumdelta R.

Finally, the system cycle coefficient 3 sets up the cycle time for thesysteml During each cycle, the system will take the necessarymeasurements, compute the ratio, .take into account the parameters a f,and provide a correction if necessary before it will then repeat itscycle. The system provides an inverse relationship between the systemcycle time 3 and the line speed Xr to provide a calculation periodcorresponding to uniform web length.

FIG. ll sets forth the operational data-flow diagram of the ratiomeasurement and control unit 28 for controlling the repeat length andindicates the relationship between the. ;,various parameters. The twodigital devices 26 and 30, FIG. I, are basically tachometers includingpulse generators, providing pulse signals indicative of the speed of Xrdand Xr. The computer computes the ratio Xr,,/Xr of the two speeds. Thecycle time g for the system determines the time period for ratiomeasurement and error correction. A typical system cycle time is 10seconds for a fixed line speed at normal operating levels. The measuredratio Xr,,/Xr is compared with the set point reading a. If the twovalues are the same, the cycle is aborted and a new cycle comparison isrun within the time set by the system cycle time. Ifthere is adifference between the set point a and the measured ratio Xr,,, r. it iscompared with the dead band range 0. If the difference is within thedead band range, up corrections will be made, and the cycle will abort.lfthe difference is outside the dead band range c, then an errorcorrection will be made. A large difference (determined by parameterewill operate the alarm circuit. The amount of correction is calculatedbased upon the deviation from the set point. The mariimum delta R,parameter f, limits the error correction made during each cycle to somemaximum value. Operating conditions may be such that a false large errorsignal could be received. Rather than to permit a large speed change tobe made in a single cycle, maximum delta R holds the correction signalto a reasonable limit. If the error had been real and there had been asubstantial error in the system, the next recycle would pick the errorup again, and a constant recycling would gradually bring the system backinto control. In the above case, the control step sizes taken to gaincontrol would be based upon the limit determined maximum delta R. Thecontrol signal determines the running time of the correction motor andis dependent upon the motor voltage coefficient setting d. Thecorrection is made and the cycle terminates with a new cycle startingbased upon the system cycle coefficient 3. A continuing check andcorrection of the system is provided with the above controls. A digitalsystem is particularly useful because of its high speed of response andits precision control capability.

What is claimed is:

1. in a method for controlling the repeat pattern length on embossedmaterials, involving the steps of providing upstream processing to theweb before the embossing step, embossing the web material, and providingdownstream processing to the web of material, the improvementcomprising: sensing the line speed of the web prior to the upstreamprocessing of the web, sensing the embossing roll speed during theembossing operation, and maintaining the ratio of web speed to embossingroll speed within a preset range to provide a product at the end of thedownstream processing, which product has the repeat patterns of theembossing in a controlled repeat length.

2. In the method of claim 1, the further step of comparing the sensedspeed ratio with a fixed reference ratio and automatically providingcontrol signals to an embossing roll drive to keep the ratio within thepreset range.

3. In the method of claim 2, the further step of controlling the size ofthe control signal within preset limits.

1. In a method for controlling the repeat pattern length on embossedmaterials, involving the steps of providing upstream processing to theweb before the embossing step, Embossing the web material, and providingdownstream processing to the web of material, the improvementcomprising: sensing the line speed of the web prior to the upstreamprocessing of the web, sensing the embossing roll speed during theembossing operation, and maintaining the ratio of web speed to embossingroll speed within a preset range to provide a product at the end of thedownstream processing, which product has the repeat patterns of theembossing in a controlled repeat length.
 2. In the method of claim 1,the further step of comparing the sensed speed ratio with a fixedreference ratio and automatically providing control signals to anembossing roll drive to keep the ratio within the preset range.
 3. Inthe method of claim 2, the further step of controlling the size of thecontrol signal within preset limits.